ZF reveals new fully active chassis system

ZF has revealed its new fully active chassis system, sMotion, which reduces inconvenient car body movements caused by potholes, bumps or curves.

The advantages of highly automated and autonomous driving of the future are a reality today – vehicle occupants can work or relax undisturbed while traveling. The company says in sMotion an intelligent actuator actively controls individual wheels, adapting piston compression and rebound for each traveling situation and road condition. sMotion also offers vehicle manufacturers modular scalability as well as component dimensions and interfaces, making it easy to tailor and integrate the system into vehicle designs.

“When it comes to the development of highly automated and autonomous driving, the chassis plays a key role,” says Dr. Holger Klein, head of the Car Chassis Technology Division at ZF. “Because by the time the autopilot takes over the wheel, all passengers want to be completely relaxed and unaware of the vehicle's movement, regardless of what is happening on the road. Our sMOTION fully active chassis system can fulfill this desire.”

SMotion is a scalable modular system based on innovative development of the company's established CDC damping system.

With ZF's intelligent sMotion shock absorbers, it is possible to eliminate almost all annoying motion and vibration from the roadway surface. “Passengers have the sensation of floating serenely over bumps and hollows,” says Dr Klein. ZF's innovation not only eliminates shocks caused by large potholes or unevenness but is equally effective against the pitching forward or back during deceleration and acceleration or the rolling and tilting when cornering or changing lanes.

Bouncing movement under control
The special feature of the sMotion system is a very compact, external electric-motor pump unit with integrated electronics, which works as a bi-directional actuator on each wheel. This actuator can actively raise and lower the piston rod and subsequently each wheel individually, a function that is unique in today's market.

This ZF technology gives optimal control over all low-frequency car body movement: When cornering, for example, the two inner wheels can be retracted and the outer ones extended enabling the car to remain virtually horizontal. The same applies to long stretches of road bumps – regardless of whether they extend over the entire width of the lane, have different characteristics on the left and right or occur only on one side.

Networked with environmental sensors such as cameras, the sMotion system can even detect road conditions in advance, such as potholes, and prepare the actuators (predictive control): When traveling over the detected road depression, this innovative technology actively keeps the affected wheel at the height of the road surface instead of allowing it to drop, as would be the case with a conventional shock absorber. sMotion also features dynamic ground clearance for each specific axle or side as well as for the entire undercarriage.

sMotion also features a second unique technology: a separate hydraulic control path. This feature compensates for higher-frequency bumps caused by minor unevenness in the road surface, such as manhole covers, transverse joints, rough asphalt or gravel. This new ZF shock absorption system builds on the company’s own Continuous Damping Control (CDC) technology with independent compression and rebound stages. This technology enables even the basic design to actively and continuously vary the characteristic curve between hard (stability-oriented and dynamic) and soft (comfort-oriented).

Data to the cloud
With sensor technology and network, sMotion helps record the necessary vertical dynamic data either directly on the actuator units or via sensors in the vehicle. This information comes together in a central control unit that controls the actuators. The integrated electronics of the actuator serve to activate the electric motor, pump and CDC valves in such a way that the greatest possible calm prevails in the car body.

Transferred to the cloud, the shock absorber data can be used to inform vehicles following behind, or even specialist agencies, about dangerous road surface damage. In addition, ZF says sMotion is perfectly prepared for networking via ZF's cubiX system. This is an integrating, modular and scalable control algorithm that coordinates all active and semi-active actuators in the car. This means sMotion can operate in conjunction with ZF's electric power steering, integrated brake control (IBC), rear axle steering (AKC) and the electric axle drive system (eVD).

Also read: World's first digital car chassis technology to reach roads in 2019